1. Field of the Invention
The present invention relates to an image forming apparatus such as a copying machine, a printer, a facsimile, or a multifunction peripheral that includes a plurality of these functions.
2. Description of the Related Art
A conventional electrophotographic image forming apparatus performs image formation through an electrophotographic process that includes charging, exposing, developing, and transferring. This charging process charges a photosensitive member to a desired potential by using a corona charger.
The corona charger includes a meshed grid electrode disposed in its shield opening to set a surface potential of the photosensitive member to a desired potential. Due to a shape of the grid electrode, floating toner is easily deposited on an inner surface (side close to a discharging wire) of the grid electrode. Deposition of a great amount of such foreign objects on the inner surface of the grid electrode causes a charging failure in the inner surface. As a result, image density unevenness may occur.
Thus, Japanese Patent Application Laid-Open No. 2006-362960 discusses a technology for preventing deposition of a great amount of toner on a grid electrode by providing a cleaner configured to clean an inner surface of the grid electrode. Specifically, the cleaner cleans the inner surface of the grid electrode by bringing a cleaning brush into contact with the inner surface of the grid electrode and reciprocating the cleaning brush in a longitudinal direction of the grid electrode.
However, in the case of the cleaner for cleaning the inner surface of the grid electrode discussed in Japanese Patent Application Laid-Open No. 2006-362960, the following problem is inevitable. The toner stuck to the inner surface of the grid electrode slides to be rubbed by the cleaning brush, thereby passing through mesh openings to an outer surface (side close to the photosensitive member) of the grid electrode.
The cleaner discussed in Japanese Patent Application Laid-Open No. 2006-362960 cannot remove the toner that has passed through the mesh openings of the grid electrode to the outer surface to be deposited. Hence, a charging failure may occur.
Providing a cleaner for cleaning the outer surface of the grid electrode may enable prevention of this problem.
However, the corona charger for improving charging efficiency is disposed extremely close (gap is about 1 mm) to the photosensitive member, and hence this arrangement may not be a practical solution to the problem.